North Korea warns of nuclear 'sacred war'

North Korea says it will use its "nuclear deterrent" in response to joint US-South Korean military exercises this weekend.

Pyongyang was ready to launch a "retaliatory sacred war" at any time, the state-run Korean Central News Agency (KCNA) said.

The BBC's John Sudworth, in Seoul, says this is not the first time that North Korea has issued such a warning.